The present invention relates generally to the field of mass transfer and specifically to vertical column contactors wherein a solid-liquid system is intermixed to effect the transfer of a given solute material from either the solid or the liquid. The term solute refers to the material being transferred from solid to liquid or from liquid to solid.
Prior art processes and equipment used in vertical column contactors have long been known. However, among the various prior designs, each have certain undesirable characteristics which reduce their efficiency and/or effectiveness and provide significantly less than optimum operation.
The most desirable characteristics for a vertical column contactor can be summarized as follows:
1. The solid and liquid flow should be countercurrent. PA1 2. Both the solid the liquid flow through the column should exhibit a high degree of plug flow, that is a first in-first out basis. Thus, there should be very little, if any, vertical mixing within the column of materials as they pass through the column to assure uniform treatment. PA1 3. The rate of flow of the solid and liquid should be as uniform as possible. Surges or rapid changes in the flow rate should be avoided as well as introduction of any gas or vapors into the mass transfer zone from any source. PA1 4. In many applications, the solids should be handled in a gentle manner to avoid undue particle size degradation by crushing or abrasive forces particularly in applications wherein the solid is intended to be used after it has been washed in the process. PA1 5. The cost of capital equipment should be minimized without sacrificing the high degree of performance characteristics.
The prior art vertical column devices tend to operate satisfactorily relative to one or more of these characteristics, however, none function in a manner to exhibit all of these characteristics to a satisfactory degree.
Prior to the present invention, no prior art vertical column contactor has provided for a continuous operation which exhibits a high degree of plug flow, gentle handling of the solids and also is capable of approaching the most efficient transfer in a significantly improved economically practical manner.